The present invention relates generally to a digital gain control apparatus and is directed more particularly to a digital gain control apparatus suitable to be made as a one chip integrated circuit.
In the art, an audio pre-amplifier is formed of a function selector (phono-tuner-AUX), a volume control circuit, a stereo-monaural mode change-over circuit, a stereo balancer, a bass/treble tone control circuit and so on. In this case, since a number of change-over circuits and resistors are required, it is difficult to make the audio pre-amplifier as an IC (integrated circuit).
Recently, instead of a mechanical switch serving as a change-over circuit, a semiconductor element such as an MOS FET has been practically used for switching a signal with a wide dynamic range without causing any distortion; also a micro-processor has been used widely for complicated signal processings.
However, an audio pre-amplifier to be used in combination with a digital control IC such as a micro processor has not been made as a one chip IC.